The implantation of mammalian embryos at the blastocysts stage is crucial for the normal development of the embryo. Impaired implantation and subsequent formation of the placenta in early pregnancy is thought to be the leading cause of preeclampsia that causes fetal and neonatal morbidity and mortality and can lead to an increased risk of cardiovascular disease. This complex implantation process involves the blastocyst's apposition to the uterine epithelium, its attachment, followed by its subsequent invasion of the uterine epithelium and interaction with the stroma cells of the uterus and finally the establishment of the placenta.
In vitro fertilization (IVF) of human eggs is a technique that involves the fertilization of eggs harvested from the uterus and the subsequent transfer of the fertilized eggs (embryos) to the uterus that will continue to develop the embryo. IVF has resulted in millions of babies born to couples who were previously infertile. This technology is practiced in fertility clinics around the world and though its efficiency has improved, it is still not highly efficient. According to the American pregnancy association (http://americanpregnancy.org/corp-sponsors/fairhaven-healthImplantation) the number of live births from IVF is 30-35% for women under 35, but drops to 6-10% in women over 40. The reason for this is a combination of the quality of the embryo that has been fertilized in vitro and its ability to implant and thrive in the uterus of the mother.
Current IVF protocols include the culturing of human embryos in the laboratory until the embryo reaches the blastocyst stage. However only a small subset of the blastocysts transferred to the mother actually implant and develop further. Most of the blastocysts fail to attach properly to the uterus and are essentially lost after the transference. As such, in order to obtain a higher pregnancy rate per IVF cycle, it is currently conventional practice to transfer multiple embryos to the mother. This procedure has the undesirable effect of rendering multiple pregnancies (IVF twins, triplets etc.) in many occasions and the associated health cost of multiple pregnancies. According to the CDC (http://www.cdc.gov/art/preparingforart/eset.htm), multiple births increase the risk of premature birth and low birth weight in infants. There is therefore a desire to find a more effective and efficient IVF technique that facilitates the implantation of the embryo to the mother uterus, thereby reducing the number of embryos transferred to the mother per cycle.